許多掘金朋友在上一篇留言，說要封裝下最新版倔监，所以這篇把封裝思路寫下，大家可以自己封裝菌仁。有好的想法也可以去github提request浩习，也感謝WingCH的貢獻(xiàn)

分析需求

為什么要封裝？

• 全局token驗(yàn)證

• 自定義攔截器

• 緩存處理

• 統(tǒng)一封裝業(yè)務(wù)錯誤邏輯

• 代理配置

• 重試機(jī)制

• log輸出

• 自定義解析济丘，數(shù)據(jù)脫殼

要初始化哪些配置谱秽？

• 域名
• 代理地址
• cookie本地緩存地址
• 超時時間
• 自定義攔截器

定義一個配置信息類去初始化這些配置：

// dio 配置項(xiàng)
class HttpConfig {
  final String? baseUrl;
  final String? proxy;
  final String? cookiesPath;
  final List<Interceptor>? interceptors;
  final int connectTimeout;
  final int sendTimeout;
  final int receiveTimeout;

  HttpConfig({
    this.baseUrl,
    this.proxy,
    this.cookiesPath,
    this.interceptors,
    this.connectTimeout = Duration.millisecondsPerMinute,
    this.sendTimeout = Duration.millisecondsPerMinute,
    this.receiveTimeout = Duration.millisecondsPerMinute,
  });

  // static DioConfig of() => Get.find<DioConfig>();
}

請求差異化有哪些配置？

• 解析策略

  許多公司接口規(guī)范經(jīng)歷過變更摹迷，有多個返回類型疟赊，那么就需要針對不同的數(shù)據(jù)類型，做不同的解析峡碉。

  比如舊版本：

  // 舊版本
  {
      "code": 1,
      "data": {},
      "state": true
  }
  // 新版本
  {
      "code": 1,
      "data": {
        "data": {},
        "hasmore":false
      },
      "message": “success”
  }
  

  要做到脫殼近哟，拿到解析后的data，就需要兩種解析策略鲫寄。所以需要根據(jù)不同接口動態(tài)配置解析策略吉执。

• path

• 參數(shù)

• cancelToken

• dio 的常用參數(shù)

  Dio 的請求參數(shù)已經(jīng)很全面的包括了分析出的配置參數(shù)，只需要另添加一個解析策略即可地来。

  遵守 SOLID 原則定義一個抽象解析策略：

  /// Response 解析
  abstract class HttpTransformer {
    HttpResponse parse(Response response);
  }
  
  

  根據(jù)實(shí)際需求默認(rèn)實(shí)現(xiàn)：

  class DefaultHttpTransformer extends HttpTransformer {
  // 假設(shè)接口返回類型
  //   {
  //     "code": 100,
  //     "data": {},
  //     "message": "success"
  // }
    @override
    HttpResponse parse(Response response) {
      // if (response.data["code"] == 100) {
      //   return HttpResponse.success(response.data["data"]);
      // } else {
      // return HttpResponse.failure(errorMsg:response.data["message"],errorCode: response.data["code"]);
      // }
      return HttpResponse.success(response.data["data"]);
    }
  
    /// 單例對象
    static DefaultHttpTransformer _instance = DefaultHttpTransformer._internal();
  
    /// 內(nèi)部構(gòu)造方法戳玫，可避免外部暴露構(gòu)造函數(shù)，進(jìn)行實(shí)例化
    DefaultHttpTransformer._internal();
  
    /// 工廠構(gòu)造方法未斑，這里使用命名構(gòu)造函數(shù)方式進(jìn)行聲明
    factory DefaultHttpTransformer.getInstance() => _instance;
  }
  

  單例模式是為了避免多次創(chuàng)建實(shí)例咕宿。方便下一步使用。

異常處理

異常大體分為以下幾種：

• 網(wǎng)絡(luò)異常
• 客戶端請求異常
• 服務(wù)端異常

客戶端異常又可拆分兩種常見的異常：請求參數(shù)或路徑錯誤，鑒權(quán)失敗/token失效

異常歸檔后創(chuàng)建異常：

class HttpException implements Exception {
  final String? _message;

  String get message => _message ?? this.runtimeType.toString();

  final int? _code;

  int get code => _code ?? -1;

  HttpException([this._message, this._code]);

  String toString() {
    return "code:$code--message=$message";
  }
}

/// 客戶端請求錯誤
class BadRequestException extends HttpException {
  BadRequestException({String? message, int? code}) : super(message, code);
}
/// 服務(wù)端響應(yīng)錯誤
class BadServiceException extends HttpException {
  BadServiceException({String? message, int? code}) : super(message, code);
}



class UnknownException extends HttpException {
  UnknownException([String? message]) : super(message);
}

class CancelException extends HttpException {
  CancelException([String? message]) : super(message);
}

class NetworkException extends HttpException {
  NetworkException({String? message, int? code}) : super(message, code);
}

/// 401
class UnauthorisedException extends HttpException {
  UnauthorisedException({String? message, int? code = 401}) : super(message);
}

class BadResponseException extends HttpException {
  dynamic? data;

  BadResponseException([this.data]) : super();
}

返回數(shù)據(jù)類型

返回的數(shù)據(jù)類型府阀，需要有成功或是失敗的標(biāo)識缆镣，還需要脫殼后的數(shù)據(jù)，如果失敗了试浙，也需要失敗的信息费就，定義幾個工廠方法方便創(chuàng)建實(shí)例：

class HttpResponse {
  late bool ok;
  dynamic? data;
  HttpException? error;

  HttpResponse._internal({this.ok = false});

  HttpResponse.success(this.data) {
    this.ok = true;
  }

  HttpResponse.failure({String? errorMsg, int? errorCode}) {
    this.error = BadRequestException(message: errorMsg, code: errorCode);
    this.ok = false;
  }

  HttpResponse.failureFormResponse({dynamic? data}) {
    this.error = BadResponseException(data);
    this.ok = false;
  }

  HttpResponse.failureFromError([HttpException? error]) {
    this.error = error ?? UnknownException();
    this.ok = false;
  }
}

開始封裝

配置 Dio

Dio 配置組裝，需要我們定義一個初始化類川队，用于把請求的初始化配置添加進(jìn)去力细。一般可以定義一個單例類，init方法里去初始化一個 Dio 固额，也可以采用實(shí)現(xiàn) Dio 的方式：

class AppDio with DioMixin implements Dio {
  AppDio({BaseOptions? options, HttpConfig? dioConfig}) {
    options ??= BaseOptions(
      baseUrl: dioConfig?.baseUrl ?? "",
      contentType: 'application/json',
      connectTimeout: dioConfig?.connectTimeout,
      sendTimeout: dioConfig?.sendTimeout,
      receiveTimeout: dioConfig?.receiveTimeout,
    );
    this.options = options;

    // DioCacheManager
    final cacheOptions = CacheOptions(
      // A default store is required for interceptor.
      store: MemCacheStore(),
      // Optional. Returns a cached response on error but for statuses 401 & 403.
      hitCacheOnErrorExcept: [401, 403],
      // Optional. Overrides any HTTP directive to delete entry past this duration.
      maxStale: const Duration(days: 7),
    );
    interceptors.add(DioCacheInterceptor(options: cacheOptions));
    // Cookie管理
    if (dioConfig?.cookiesPath?.isNotEmpty ?? false) {
      interceptors.add(CookieManager(
          PersistCookieJar(storage: FileStorage(dioConfig!.cookiesPath))));
    }

    if (kDebugMode) {
      interceptors.add(LogInterceptor(
          responseBody: true,
          error: true,
          requestHeader: false,
          responseHeader: false,
          request: false,
          requestBody: true));
    }
    if (dioConfig?.interceptors?.isNotEmpty ?? false) {
      interceptors.addAll(interceptors);
    }
    httpClientAdapter = DefaultHttpClientAdapter();
    if (dioConfig?.proxy?.isNotEmpty ?? false) {
      setProxy(dioConfig!.proxy!);
    }
  }

  setProxy(String proxy) {
    (httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate =
        (client) {
      // config the http client
      client.findProxy = (uri) {
        // proxy all request to localhost:8888
        return "PROXY $proxy";
      };
      // you can also create a HttpClient to dio
      // return HttpClient();
    };
  }
}

Restful請求

采用 Restful 標(biāo)準(zhǔn)眠蚂，創(chuàng)建對應(yīng)的請求方法：

class HttpClient {
  late AppDio _dio;

  HttpClient({BaseOptions? options, HttpConfig? dioConfig})
      : _dio = AppDio(options: options, dioConfig: dioConfig);

  Future<HttpResponse> get(String uri,
      {Map<String, dynamic>? queryParameters,
      Options? options,
      CancelToken? cancelToken,
      ProgressCallback? onReceiveProgress,
      HttpTransformer? httpTransformer}) async {
    try {
      var response = await _dio.get(
        uri,
        queryParameters: queryParameters,
        options: options,
        cancelToken: cancelToken,
        onReceiveProgress: onReceiveProgress,
      );
      return handleResponse(response, httpTransformer: httpTransformer);
    } on Exception catch (e) {
      return handleException(e);
    }
  }

  Future<HttpResponse> post(String uri,
      {data,
      Map<String, dynamic>? queryParameters,
      Options? options,
      CancelToken? cancelToken,
      ProgressCallback? onSendProgress,
      ProgressCallback? onReceiveProgress,
      HttpTransformer? httpTransformer}) async {
    try {
      var response = await _dio.post(
        uri,
        data: data,
        queryParameters: queryParameters,
        options: options,
        cancelToken: cancelToken,
        onSendProgress: onSendProgress,
        onReceiveProgress: onReceiveProgress,
      );
      return handleResponse(response, httpTransformer: httpTransformer);
    } on Exception catch (e) {
      return handleException(e);
    }
  }

  Future<HttpResponse> patch(String uri,
      {data,
      Map<String, dynamic>? queryParameters,
      Options? options,
      CancelToken? cancelToken,
      ProgressCallback? onSendProgress,
      ProgressCallback? onReceiveProgress,
      HttpTransformer? httpTransformer}) async {
    try {
      var response = await _dio.patch(
        uri,
        data: data,
        queryParameters: queryParameters,
        options: options,
        cancelToken: cancelToken,
        onSendProgress: onSendProgress,
        onReceiveProgress: onReceiveProgress,
      );
      return handleResponse(response, httpTransformer: httpTransformer);
    } on Exception catch (e) {
      return handleException(e);
    }
  }

  Future<HttpResponse> delete(String uri,
      {data,
      Map<String, dynamic>? queryParameters,
      Options? options,
      CancelToken? cancelToken,
      HttpTransformer? httpTransformer}) async {
    try {
      var response = await _dio.delete(
        uri,
        data: data,
        queryParameters: queryParameters,
        options: options,
        cancelToken: cancelToken,
      );
      return handleResponse(response, httpTransformer: httpTransformer);
    } on Exception catch (e) {
      return handleException(e);
    }
  }

  Future<HttpResponse> put(String uri,
      {data,
      Map<String, dynamic>? queryParameters,
      Options? options,
      CancelToken? cancelToken,
      HttpTransformer? httpTransformer}) async {
    try {
      var response = await _dio.put(
        uri,
        data: data,
        queryParameters: queryParameters,
        options: options,
        cancelToken: cancelToken,
      );
      return handleResponse(response, httpTransformer: httpTransformer);
    } on Exception catch (e) {
      return handleException(e);
    }
  }

  Future<Response> download(String urlPath, savePath,
      {ProgressCallback? onReceiveProgress,
      Map<String, dynamic>? queryParameters,
      CancelToken? cancelToken,
      bool deleteOnError = true,
      String lengthHeader = Headers.contentLengthHeader,
      data,
      Options? options,
      HttpTransformer? httpTransformer}) async {
    try {
      var response = await _dio.download(
        urlPath,
        savePath,
        onReceiveProgress: onReceiveProgress,
        queryParameters: queryParameters,
        cancelToken: cancelToken,
        deleteOnError: deleteOnError,
        lengthHeader: lengthHeader,
        data: data,
        options: data,
      );
      return response;
    } catch (e) {
      throw e;
    }
  }
}

響應(yīng)解析

得到請求數(shù)據(jù)后，解析為定義的通用返回數(shù)據(jù)類型斗躏，需要首先判斷是否取得返回值逝慧，然后判斷網(wǎng)絡(luò)請求成功，網(wǎng)絡(luò)請求成功之后啄糙，采取判斷是否接口返回期望的數(shù)據(jù)笛臣，還是因?yàn)檎埱髤?shù)錯誤或者服務(wù)器錯誤返回了錯誤信息。如果錯誤了隧饼，把錯誤信息格式化為定義的異常：

HttpResponse handleResponse(Response? response,
    {HttpTransformer? httpTransformer}) {
  httpTransformer ??= DefaultHttpTransformer.getInstance();

  // 返回值異常
  if (response == null) {
    return HttpResponse.failureFromError();
  }

  // token失效
  if (_isTokenTimeout(response.statusCode)) {
    return HttpResponse.failureFromError(
        UnauthorisedException(message: "沒有權(quán)限", code: response.statusCode));
  }
  // 接口調(diào)用成功
  if (_isRequestSuccess(response.statusCode)) {
    return httpTransformer.parse(response);
  } else {
    // 接口調(diào)用失敗
    return HttpResponse.failure(
        errorMsg: response.statusMessage, errorCode: response.statusCode);
  }
}

HttpResponse handleException(Exception exception) {
  var parseException = _parseException(exception);
  return HttpResponse.failureFromError(parseException);
}

/// 鑒權(quán)失敗
bool _isTokenTimeout(int? code) {
  return code == 401;
}

/// 請求成功
bool _isRequestSuccess(int? statusCode) {
  return (statusCode != null && statusCode >= 200 && statusCode < 300);
}

HttpException _parseException(Exception error) {
  if (error is DioError) {
    switch (error.type) {
      case DioErrorType.connectTimeout:
      case DioErrorType.receiveTimeout:
      case DioErrorType.sendTimeout:
        return NetworkException(message: error.error.message);
      case DioErrorType.cancel:
        return CancelException(error.error.message);
      case DioErrorType.response:
        try {
          int? errCode = error.response?.statusCode;
          switch (errCode) {
            case 400:
              return BadRequestException(message: "請求語法錯誤", code: errCode);
            case 401:
              return UnauthorisedException(message: "沒有權(quán)限", code: errCode);
            case 403:
              return BadRequestException(message: "服務(wù)器拒絕執(zhí)行", code: errCode);
            case 404:
              return BadRequestException(message: "無法連接服務(wù)器", code: errCode);
            case 405:
              return BadRequestException(message: "請求方法被禁止", code: errCode);
            case 500:
              return BadServiceException(message: "服務(wù)器內(nèi)部錯誤", code: errCode);
            case 502:
              return BadServiceException(message: "無效的請求", code: errCode);
            case 503:
              return BadServiceException(message: "服務(wù)器掛了", code: errCode);
            case 505:
              return UnauthorisedException(
                  message: "不支持HTTP協(xié)議請求", code: errCode);
            default:
              return UnknownException(error.error.message);
          }
        } on Exception catch (_) {
          return UnknownException(error.error.message);
        }

      case DioErrorType.other:
        if (error.error is SocketException) {
          return NetworkException(message: error.message);
        } else {
          return UnknownException(error.message);
}
      default:
        return UnknownException(error.message);
    }
  } else {
    return UnknownException(error.toString());
  }
}

緩存沈堡、重試、401攔截

默認(rèn)的通用攔截器在 AppDio里直接定義燕雁，如果需要額外配置的攔截器诞丽，從HttpConfig里傳入。

這些攔截器的創(chuàng)建拐格，可以參考上一篇強(qiáng)大的dio封裝僧免，可能滿足你的一切需要,這里就不再贅述。

使用

第一步捏浊，全局配置并初始化：

  HttpConfig dioConfig =
      HttpConfig(baseUrl: "https://gank.io/", proxy: "192.168.2.249:8888");
  HttpClient client = HttpClient(dioConfig: dioConfig);
  Get.put<HttpClient>(client);

請求：

  void get() async {
    HttpResponse appResponse = await dio.get("api/v2/banners");
    if (appResponse.ok) {
      debugPrint("====" + appResponse.data.toString());
    } else {
      debugPrint("====" + appResponse.error.toString());
    }
  }

附上開發(fā)環(huán)境：

[?] Flutter (Channel stable, 2.0.5, on Mac OS X 10.15.7 19H15 darwin-x64, locale zh-Hans-CN)